Conventional gas meters which measure the volume of flowing gas by mechanical means require correction because they do not take into account the effect of pressure and temperature on volume. Specifically, the combination of Charles and Boyle's laws, supplemented by a supercompressibility factor, indicates that the volume is more accurately given by: EQU V=Vm/.times.(Pm/Pb).times.(Tb/Tm).times.Z
where
Vm is the measured uncorrected volume obtained from the meter at line pressure and line temperature, PA1 Pm is the measured line pressure of the flowing gas, PA1 Tm is the measured line temperature of the flowing gas, PA1 Pb is the base pressure of 14.73 psia or other value in absolute units, depending on the applicable protocol, PA1 Tb is the base temperature of 60 degrees F. in absolute units, or other value, depending on the applicable protocol, and PA1 Z is the square of the supercompressibility factor.
The present invention is directed to a simple method of calculating the corrected volume according to the above formula, and to a compact, low power device for carrying out that method.
Electronic volume correction devices are typically employed in remote and harsh environments which demand special accomodation. Safety is a primary consideration, so that the electrical and thermal power of such devices should be minimized to reduce the possibility of igniting the gas. The employment of microprocessors and memories, as found in some devices, are more costly and require more power than the present invention. The employment of analog dividers for obtaining the ratio Pm/Tm, as found in some devices, requires extra circuitry and power to maintain stability in varying ambient conditions. Furthermore, for battery powered devices in remote areas, it is advantageous to minimize power consumption to reduce the frequency of manual replacement of batteries. It is therefore desirable to have a reliable electronic device manufactured from a minimum of inexpensive components which consume little power.